A chronic electrical stimulator, such as a cardiac stimulator, can be implanted to deliver medical therapy. Examples of cardiac stimulators include implantable cardiac rhythm management (CRM) device such as pacemakers, implantable cardiac defibrillators (ICDs), and implantable devices capable of performing pacing and defibrillating functions.
A CRM device, such as an implantable pacemaker, is typically an implantable device that can provide electrical stimulation to selected chambers of the heart in order to treat disorders of cardiac rhythm. In an example, the implantable pacemaker is a CRM device that can pace the heart with timed pacing pulses, thereby establishing an appropriate cardiac rhythm, such as by enforcing a minimum heart rate, in order to meet a metabolic demand. In an example, the CRM device can deliver synchronized pacing pulses to different areas of the heart in order to coordinate contractions. Coordinated contractions can allow the heart to pump efficiently while providing sufficient cardiac output.
Heart failure generally refers to a clinical syndrome in which cardiac function causes a below normal cardiac output that can fall below a level adequate to meet the metabolic demand of peripheral tissues. Heart failure can present itself as congestive heart failure (CHF) due to the accompanying venous and pulmonary congestion. Heart failure can be due to a variety of etiologies such as ischemic heart disease.
Blood pressure generally refers to the force exerted on the walls of blood vessels by circulating blood, and can be indicative of the amount of work that the heart must do in order to circulate blood through the circulatory system of a subject. Hypertension generally refers to an elevated blood pressure, whereas hypotension generally refers to a low blood pressure.
Hypertension is a cause of heart disease and other related cardiac co-morbidities. Hypertension can occur when blood vessels constrict. As a result, the heart works harder to maintain flow at a higher blood pressure, which can contribute to heart failure. A large segment of the general population, as well as a large segment of patients implanted with pacemakers or defibrillators, suffer from hypertension. The long term mortality as well as the quality of life can be improved for this population if blood pressure and hypertension can be reduced. Many patients who suffer from hypertension do not respond to treatment, such as treatments related to lifestyle changes and hypertension drugs.
Hypotension can be indicative of various physiological states, such as: a reduced blood volume, which can result from a loss of blood or other fluids; a decreased cardiac output, which can result from CHF, myocardial infarction (MI), or a low heart rate; or excessive vasodilation or insufficient constriction of the resistance blood vessels due to decreased sympathetic nervous system output or increased parasympathetic activity.